Ordinary vehicles travel taking the power out of an internal combustion engine using gasoline as fuel, and such vehicles have an on-board refrigeration circuit, and the cooling is performed by evaporating refrigerant in an evaporator for performing the cooling, and cooling the car interior air by the generated cold heat.
In addition, the heating is performed by heating the car interior air by the heat of the cooling water for cooling the engine.
Nonetheless, as such vehicles take out the driving force through combustion of gasoline or others, the control or regulation of hazardous materials contained in the exhaust gas thereof comes to be desired zealously.
Moreover, conventionally, as refrigerant for cooling and refrigeration apparatus, for instance, chlorodifluoromethane (R22, boiling point −40.8° C.) or the like have been used. However, R22 or the like become the object of the fluorine regulation because they destroy the ozone layer by their high latency of ozone destruction, when they are released in the atmosphere and attain the ozone layer in the upper air of the Earth.
The destruction of this ozone layer is provoked by chlorine group (Cl) in the refrigerant. There, refrigerants not containing chlorine group, for example, alternative refrigerants such as difluoromethane (HFC-32, R32, boiling point −52° C.) or others have been proposed; however, they ended up by being included in gases to be regulated by The 3rd Session of the Conference of the Parties to the United Nations Framework Convention on Climate Change, Kyoto, 1997, because Global Warming Potential (GWP) is 1300 to 1900, and their use comes to be difficult.
In such trend of attaching importance to the environment, natural refrigerants such as CO2 or others existing in the natural world and imposing less load to the environment attract attention, because they are free from ozone layer destruction effect, combustibility or toxicity and, furthermore, they are extremely friendly to the environment as their global warming potential (GWP) is 1, and in addition, they are economical.
Nonetheless, in case of applying CO2 refrigerant to a refrigeration circuit, as a high operation pressure equal or superior to 3 times (for instance, 10 megapascals) compared to the refrigerant for air-conditioner of the prior art is required, there is a problem of closness of the compression chamber in the single stage compression system compressor structure of the prior art, and for example, it can only compress to the level of 6 megapascals, and there was a problem that CO2 could not be used as refrigerant.
There, a two-stage compression system compressor for compressing CO2 from 3 megapascals to 6 megapascals (intermediate pressure) in the first stage and, further, compressing from 6 megapascals to 10 megapascals in the second stage before discharging has been proposed.
It has been proposed to use CO2 as refrigerant for hybrid cars and idle stop coping cars taking electricity and gasoline as energy source, battery cars taking only electricity as energy source, or other vehicles, perform the cooling by loading a refrigeration circuit provided with a two-stage compression system compressor driven by electricity, and perform the heating, on the other hand, by the heat of the chilled water for cooling the engine.
Whatsoever, the waste heat of such vehicles is low, and there was a problem that a sufficient heating could not be performed.
It is an object of the present invention to provide an on-vehicle air-conditioner that can solve problems of the prior art, and perform effectively cooling, heating, dehumidification, or others, even in case of using CO2 refrigerant, in vehicles of low waste heat, such as hybrid cars taking electricity and gasoline as energy source, idle stop coping cars or battery cars taking only electricity as energy source, or other vehicles.